JPS6336058A - Air-fuel ratio controlling method for liquefied gas engine - Google Patents

Abstract

PURPOSE:To prevent a mixture from becoming highly thick due to a liquefied gas which becomes highly dense by opening an air control valve at a defined duty ratio and feeding air into an intake system at the time of an idling operation and prior to the completion of warming up, when feeding an engine with a pressure reduced and vaporized liquefied gas. CONSTITUTION:A liquefied gas in a pressure container 1 is introduced into a vaporizer 4 through a passage 3 having a closing valve 2 and vaporized with its pressure being reduced and, then, is fed into an intake passage 10 through a nozzle 9 provided on the venturi 8 of a mixing device 7 via a passage 6 having a throttle 5. In this case, an intake passage 19 having an air control valve 18 is connected to the lower course side of the throttle valve 17 of an intake system 11. The air control valve 18 is controlled in its opening and closing by a control unit 16 based on the detected signals of the position sensor 20 of the throttle valve 17 and the temp. sensor 22 of the cooling water 21 of an engine 13. Thereby, at the time of an idling operation and prior to the completion of warming up, the air control valve 18 is opened at a defined duty ratio to feed air into the intake system 11.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an air-fuel ratio control method for an engine that uses liquefied gas such as LPG as fuel, and is commonly used in liquefied gas engines of automobiles. Ru.

As is well known, the fuel system that supplies chloride gas to the plant is
The structure is such that liquefied gas is taken out of a pressure-resistant container, vaporized under reduced pressure by a vaporizer, and sent to a mixer installed in the intake system. In such fuel systems, in order to promote the vaporization of liquefied gas, it is widely practiced to guide engine cooling water to a vaporizer and heat it.
Drawings such as Japanese Patent No. 98 and Japanese Utility Model Publication No. 55-4536 also show that cooling water is circulated to the primary chamber side of the vaporizer.

As mentioned above, in a fuel system equipped with a vaporizer heated by engine cooling water, if the air-fuel ratio during idling is adjusted to the appropriate level after warm-up is completed, During idle operation, relatively low-temperature cooling water is guided to the vaporizer, so the vaporized liquefied gas also has a relatively low temperature, and even if the pressure is adjusted to a constant pressure, it has a higher density than when it is at a high temperature after warm-up. becomes. Further, during idle operation, the negative pressure in the mixer is extremely low, so the liquefied gas in the vaporizer is pushed out toward the mixer instead of being sucked out by the negative pressure in the vaporizer.

(2) In this case, a higher density and thus a larger amount of liquefied gas is sent to the intake system than when the af4 is adjusted, and the air-fuel ratio becomes smaller. When the engine temperature is sufficiently low, enriching the air-fuel mixture is preferable in order to maintain idling operation, but this tends to cause problems in terms of exhaust gas regulations. In addition, when the temperature of the cooling water in a semi-warmed-up state is around 40 to 60°C, more acclimatization gas than is required is sent even though the air-fuel ratio is preferably almost the same as after warm-up is completed. Therefore, not only is it impossible to reduce harmful substances in exhaust gas, but it also has a negative effect on the stability of idling operation.

Therefore, the present invention was invented with the object of providing a means for correcting the air-fuel mixture to an appropriate air-fuel ratio during idling operation before the warm-up period is completed.

The present invention provides an air control valve to vaporize liquefied gas in a pressure-resistant container under reduced pressure in a vaporizer heated with industrial cooling water and send it to a mixer installed in the intake system to supply it to the engine. The air passage is connected to the intake system.

When the temperature of the cooling water is detected and it is determined that the warm-up is not completed during idling operation, the air 1 control valve is opened and closed at a duty ratio set according to the temperature of the cooling water. The above problem is solved by introducing air into the intake system.

The liquefied gas discharged from the working pressures 85 and 9 is vaporized under reduced pressure in a vaporizer, adjusted to a constant pressure slightly lower than atmospheric pressure, and sent to the mixer.

The temperature of the engine's cooling water is constantly detected by a temperature sensor and input to the electronic control unit, and whether the engine is running at idle or not is determined by the electrical signal input to the control unit based on the position of the throttle valve. be done. When it is determined based on the electrical signal from the temperature control unit that warm-up is not completed, a drive signal is sent from the control unit to the air control valve only during idle operation.

The drive signal is formed by a pulse signal with a duty ratio set in advance according to the temperature of the cooling water.

For example, assume the duty ratio characteristic as shown in FIG. The air control valve driven by this drive signal introduces air controlled according to the duty ratio into the intake system, and the air-fuel ratio of the mixture supplied to the engine is as shown by the solid line in Figure 3. In a state where it is determined that the temperature is below a preset temperature and is not yet completed slowly, the temperature is corrected to be larger than that of the conventional system, which is indicated by a broken line.

Note that the drive signal is determined to open and close the air control valve when it is at least in the half-Ill state.

According to the present invention, in the fuel system where the engine cooling water is introduced into the vaporizer to warm the liquefied gas, promote its vaporization, and send it to the mixer of the intake system, the cooling water of r is at a low temperature. The introduction of air prevents the mixture from becoming highly concentrated due to the low temperature and high density of the vaporized liquefied gas.In particular, in the present invention, since the amount of intake air is small, even a small change in the liquefied gas will cause the air-fuel ratio to change. The amount of air introduced during idle operation, which has a large impact on the engine speed, is controlled by the duty ratio of the air control valve opening and closing, so air is introduced according to the liquefied gas density, which fluctuates due to temperature changes.

It is possible to set an appropriate air-fuel ratio according to the temperature. In addition, it is easily possible to set the air-fuel ratio to almost the same as after warming up in a semi-warmed state where warming up has progressed considerably, and it is possible to stabilize idle operation before the end of the engine and to reduce harmful substances in exhaust gas. It is possible to appropriately measure the reduction of

Example An embodiment of the present invention will be described based on the layout diagram of FIG.

The liquefied gas in the pressure container 1 is sent to the vaporizer 4 through an introduction passage 3 having an on-off valve 2 that opens only when the engine is operating, where it is vaporized under reduced pressure and adjusted to a constant pressure slightly lower than atmospheric pressure. Setting the basic flow rate95
・The mixer 7 is fed through the fuel passage 6.
The air is sent to the intake passage 10 from a slit-shaped nozzle 9 provided in the air.

The intake system 11 has a mixer 7 and an intake manifold 12,
A mixture of liquefied gas and air is supplied to the engine 13. Further, a correction fuel A approximately 14 is provided which is branched from the upstream side of the fuel passage 60 orifice 5 and connected to the mixture 47. The correction fuel is controlled by opening and closing according to the duty ratio of the recommendation signal sent from the control unit 16, and the fuel power is increased according to the operating state of the enshiff 13.

Fuel is not increased during idling operation.

An air control valve 19 equipped with an electromagnetically driven air control valve 18 is connected to the downstream side of the bite valve 17 of the intake system 11, and the air control valve is controlled by a drive signal sent from the control unit 16. 18 is driven to open and close.The control unit 16 receives an electric signal from the throttle valve 17 position/s 20 so that it can detect whether the engine is idling or not. An electrical signal from the temperature sensor 22 is continuously input so that it can be detected whether or not warm-up has been completed.

A portion of the cooling water 21 is sent to the vaporizer 4 through a conduit 23 to heat the liquefied gas.

The air control valve 18 is then driven as described above when it is determined that the temperature is idling and has not yet warmed up to a preset temperature or below, and air is introduced into the intake system 11 to maintain the air-fuel mixture at a suitable temperature. It corrects the fuel ratio. When the warm-up is completed,
Alternatively, when the throttle valve 17 is opened before the warm-up is completed, the air control valve 18 is closed.

[Brief explanation of the drawing]

FIG. 1 is a layout diagram of an embodiment of the present invention, FIG. 2 is a duty ratio characteristic diagram of an air control valve, and FIG. 3 is an air-fuel ratio curve according to the present invention. l...Pressure container, 4...vaporizer, 7...mixing gg, ll...intake system,
13...Eng/Jin. 16... Control unit, 17... Throttle valve, 18... Air control valve, 19... Air passage, 20... Position sensor , 21...
・Cooling water, 22...Temperature sensor.

Claims (1)

[Claims] An air control valve is provided to vaporize the liquefied gas in the pressure container under reduced pressure in a vaporizer heated by engine cooling water, and send it to a mixer installed in the intake system to supply it to the engine. An air passage is connected to the intake system,
The air is controlled by opening and closing the air control valve at a duty ratio set according to the temperature of the cooling water when the temperature of the cooling water is detected and it is determined that the warm-up is not completed during idling operation. An air-fuel ratio control method for a liquefied gas engine, characterized in that the air-fuel ratio is introduced into the intake system.